The present invention relates to a carburetion arrangement for an internal combustion engine of a manually guided implement, with the arrangement including a carburetor that has an air channel, the cross-section of which is variable via a butterfly valve.
To achieve a high power, and to fulfill the respectively applicable emissions standards, manually guided implements having an internal combustion engine and a carburetor are provided with an appropriate setting of the fuel/air ratio that is set to a hot running condition of the internal combustion engine. Thus, when the internal combustion engine is started after longer periods of rest, and in particular at low ambient temperatures, the mixture prepared by the carburetor is too lean, which can lead to starting difficulties.
To improve the starting condition, especially the cold starting condition of the internal combustion engine, arrangements are known for enriching the mixture during the starting phase. For example, an increased underpressure can be produced in the intake channel by means of a starter valve that is disposed in the air channel of the carburetor upstream of the butterfly valve. As a result of the increased underpressure, an increased quantity of fuel is drawn in relative to the quantity of air that is drawn in through the internal combustion engine. The mixture becomes richer, thus improving the starting conditions. Shortly after the internal combustion engine has started, the starter valve is to be opened by the operator, thereby establishing the mixture ratio of the fuel/air mixture ratio of the fuel/air mixture that is provided for normal operation. The control of the position of the starter valve requires the attentiveness of the operator. If the starter valve is opened too late, the rich fuel/air mixture can cause the engine to die.
It is therefore an object of the present invention to provide a carburetion arrangement for an internal combustion engine of a manually guided implement with which the starting characteristics of the engine are improved.